1. Field of the Invention
The present invention relates to a fuel protective apparatus which houses and protects a fuel assembly of a light water reactor or the like, a fuel transport container which houses the fuel protective apparatus and a method of transporting the fuel assembly thereof.
In particular, the present invention relates to a fuel protective apparatus which is capable of stably housing a fuel assembly of a reactor fuel such as a mixed-oxide (MOX) fuel or the like, a fuel transport container which can stably transport the fuel protective apparatus and a method of stably transporting the fuel assembly thereof.
2. Description of the Prior Art
A reactor fuel, which is used in a light water reactor such as a boiling water reactor, a pressurized water reactor or other similar reactors, is housed and protected in a fuel protective container. By mounting the fuel protective container housing the reactor fuel in a fuel transport container, it is possible to safely transport the fuel protective container and the reactor fuel.
An explanation of a conventional fuel protective container housing a fuel assembly, for example the MOX fuel assembly or the like, as the reactor fuel is described hereinafter.
FIG. 35 shows a fuel protective container 1, when, for example, the fuel assembly is housed in the fuel protective container 1, is provided vertically on a horizontal plane P.
As shown in FIG. 35, the fuel protective container 1 wholly has a substantially cylindrical shaped construction having a substantially square shape in its lateral cross section. A longitudinal direction corresponding to an axial direction of the fuel protective container 1 is positioned along a vertical direction orthogonal to the horizontal plane P in the case where the fuel assembly is housed in the fuel protective container 1, the fuel protective container 1 is lifted so as to be mounted in the fuel transport container and the like.
When the longitudinal direction of the fuel protective container is positioned along the vertical direction orthogonal to the horizontal plane P, the fuel protective container 1 is provided with a container main body 2 comprising a substantially square shaped bottom wall portion 2a and a side wall portion 2b which is provided on three side surfaces of the bottom wall portion 2a except for one side surface thereof and extended upwards along the longitudinal direction side. The side wall portion 2b has a substantially U shape in its lateral cross section. The container main body 2 constituted by the bottom wall portion 2a and the side wall portion 2b has an upside surface and one side surface each of which is opening.
The fuel protective container 1 also has a plate-like side cap member 3 attached to the container main body 2 by means of a bolt and otherwise so as to cover the one side surface thereof which is opening so that the one side opening surface is freely opened and closed and a top portion cap member 4 removably attached to the container main body 2 by means of a bolt so as to cover the upside opening surface thereof. An interior of the fuel protective container 1 is formed with a hollow chamber (fuel housing space) 6 which has a substantially cylindrical shaped construction having a substantially square in its lateral cross section and is capable of housing a fuel assembly 5 of a reactor fuel by the container main body 2, the side cap member 3 and the top portion cap member 4.
On the other hand, the fuel assembly 5 is constructed in the following manner. Specifically, a plurality of fuel rods are tied up in a bundle with a metallic upper tie-plate 7 which has a relatively large-mass and is situated on an upper portion of the fuel rods in FIG. 35 and with a metallic lower tie-plate 8 which has a relatively large-mass and is situated on a lower portion of the fuel rods in FIG. 35 so as to form the fuel assembly 5. The bundled fuel rods (fuel rod group) constituting the fuel assembly 5 are supported by means of fuel spacers 9 with a predetermined interval.
That is, in the case of transporting the fuel assembly 5, the fuel assembly 5 is housed in the fuel housing space 6 of the fuel protective container i and the fuel protective container 1 in which the fuel assembly 5 is housed is mounted in a fuel transport container, which is not shown. Then, the fuel transport container in which the fuel protective container 1 is mounted is transported by means of fuel transport means such as a track, freight car or train, ship and so on thereby transporting the fuel assembly 5 together with the fuel protective container 1.
In the conventional fuel protective container 1, the fuel assembly 5 housed in the fuel housing space 6 of the fuel protective container I is supported by means of the container main body 2. The container main body 2 is a structural assembly which has a mechanical and physical strength enough to support an own weight of the fuel assembly 5. On the other hand, the side cap member 3 is merely a cap member which is capable of being opened and closed, and does not have the sufficient mechanical and physical strength. For this reason, it is impossible to hoist up the fuel protective container 1 by means of using the side cap member 3 in terms of the mechanical and physical strength thereof.
Meanwhile, when housing the fuel assembly 5 in the fuel protective container 1, the elongated cylindrical-shaped fuel assembly 5 is inserted into the fuel protective container I while removing the top portion cap member 4 fastened by the bolt from the container main body 2, and then, is housed in the fuel protective container 1. Thereafter, the top portion cap member 4 must be again attached onto the container main body 2 by means of the bolt; namely, a re-attachment work is required.
Further, after the fuel assembly 5 has been housed in the fuel protective container 1, when mounting the fuel protective container 1 into the fuel transport container (not shown), a jig (hoisting accessory attachment jig), such as an eyebolt (not shown) for attaching the hoisting accessory is attached to the top portion cap member 4. By making use of the hoisting accessory attachment jig, the fuel protective container 1 is hoisted up so as to mount the fuel protective container 1 into the fuel transport container. After the mounting operation of the fuel protective container 1, the hoisting accessory attachment jig must to be removed from the top portion cap member 4. Therefore, when mounting the fuel protective container 1 into the fuel transport container, for each fuel assembly 5, the top portion cap member 4 must be attached to and detached from the fuel protective container 1 and, in addition to the attachment and detachment works of the cap member 4, the hoisting accessory attachment jig eyebolt must be attached to and detached from the top portion cap member 4.
Chip The attachment and detachment works of the cap member 4 and the hoisting accessory attachment jig as described above take much working time and labor; for this reason, it is difficult to achieve a simplification and reduction of mounting work of the fuel protective container.
In addition, in order to transport a great many of fuel assemblies 5, there has been required a development of a large-capacity fuel transport container which is capable of housing a great many of fuel protective containers 1. However, the following problem arises in the development of the large-capacity fuel transport container.
That is, for safely transporting the rectangular square cylindrical shaped fuel protective container 1, the fuel protective container 1 needs to be inserted and mounted into one of a plurality of basket holes of the fuel transport container, the basket hole thereof having a larger cross sectional dimension, and then, the fuel transport container in which the fuel protective container 1 is mounted needs to be transported. In order to transport the fuel transport container and the fuel protective container 1 in a body, the fuel protective container 1 must be fixedly supported in the basket hole of the fuel transport container.
In a conventional transport container, a required space of the plurality of basket holes (basket hole group) each of which houses the fuel protective container 1 increases and there is a need of providing a fixedly supporting device which fixedly supports the fuel protective container 1 for each basket hole. In addition, a required space (bulk space) of the fixedly supporting device becomes considerably large. For this reason, it is difficult to make compact the fuel transport container which houses a great many of fuel assemblies, and this problem is a greater factor of hindering the development of the fuel transport container which has a compact structure and a large capacity.
Thus, it is strongly desired that a number of the fixedly supporting devices is decreased and the fixedly supporting device itself is made compact.
Further, in order to transport a great many of the fuel assemblies 5, a structure of the fuel transport container is employed such that a great many of fuel protective containers 1 are capable of being mounted therein. For this reason, various works necessary for mounting the great many of fuel protective containers 1 into the fuel transport container are required. For example, there are the attachment and detachment works of the top portion cap member 4, the attachment and detachment works of the hoisting accessory attachment jig, the mounting work of the fuel protective container 1, the fixedly supporting (fixing) work of the fuel protective container 1, and the like.
However, it is difficult to achieve a simplification of these works because of requiring these works for each of the fuel protective containers. Therefore, simplification and reduction of these works is strongly desired.
Meanwhile, taking an interest of the fuel protective container 1 itself mounted in the fuel transport container, the following problem arises resulting from the relationship with the fuel assembly 5 housed therein.
That is, in the conventional fuel protective containers, in order to prevent, when transporting the fuel protective container 1 in which the fuel assembly 5 is housed, a vibration of the fuel assembly 5 in the fuel protective container 1, several sets of transport (fastening) separators 10 are inserted between the fuel spacers 9, between the fuel spacer 9 and the upper tie-plate 7 and between the fuel spacer 9 and the lower tie-plate 8. Since the fuel assembly 5 is fixedly supported to the fuel protective container 1 by means of fastening forces of the fastening separators 10 based on the fastening force caused by the side cap member 3 to one side wall surface of the container main body 2, the fastening forces acting to portions of the fuel assembly 5 at which the fastening separators 10 are not attached are insufficient. That is, the fastening forces acting on both end portions of the fuel assembly 5 along the longitudinal direction thereof at which the upper-tie-plate 7 and the lower tie-plate 8 are attached, respectively, are insufficient. Therefore, resulting from the mass of the upper tie-plate 7 and the lower tie-plate 8, there is the possibility that each of the upper tie-plate 7 and the lower tie-plate 8 peculiarly vibrates as compared with the vibration of the central portion of the fuel assembly 5 according to the vibration in the horizontal direction when transporting the fuel protective container 1.
In the conventional fuel protective apparatus having the fuel protective container 1 in which the fuel assembly 5 is housed while being protected, when housing the fuel assembly 5 in the fuel protective container 1 or when mounting the fuel protective container 1 into the fuel transport container, much working time and labor is spent in attaching and detaching work of the top portion cap member 4 or the hoisting accessory attachment jig with an eyebolt or the like. For this reason, there has arisen a problem that simplification and reduction of mounting work of the fuel protective container is not achieved.
Further, when making a development of a large-capacity transport container which is capable of housing the great many of fuel assemblies, since the number of the fixedly supporting devices which fixedly support the fuel protective containers to the fuel transport container, respectively is not decreased and each of the fixedly supporting devices itself is not made compact, it is difficult to develop a compact and large-capacity fuel transport container, and to achieve a reduction of the various mounting works of the fuel protective container.
Furthermore, because the fastening forces acting on the upper tie-plate and lower tie-plate of the fuel assembly housed in the fuel protective container are insufficient, each of the upper tie-plate and the lower tie-plate peculiarly vibrates when transporting the fuel protective container thereby causing a problem of accelerating wear of the metallic contact portions of the bundled fuel rods group.